plies to the appropriate ground with a 10F tantalum
capacitor, to filter power supply noise, in parallel with a
0.1F capacitor. A combination of 0.01F in parallel
with high quality 47pF ceramic chip capacitor located
very close to the MAX105 device filters high frequency
noise. A properly designed PC board (see MAX105EV
Kit data sheet) allows the user to connect all analog
supplies and all digital supplies together thereby
requiring only two separate power sources. Decoupling
AVCC, AVCCI, AVCCQ and AVCCR with ferrite-bead
suppressors prevents further crosstalk between the
individual analog supply pins
Thermal Management
The MAX105 is designed for a thermally enhanced 80-
pin TQFP package, providing greater design flexibility,
increased thermal efficiency and a low thermal junc-
tion-case (
θjc) resistance of ≈1.26°C/W. In this pack-
MAX105
Dual, 6-Bit, 800Msps ADC with On-Chip,
Wideband Input Amplifier
______________________________________________________________________________________
17
AVCCQ
AVCC
AGNDR
AGND
AGNDI
AGNDQ
AVCCQ
AVCC
AGND
AGNDQ
AGNDI
AGNDR
AVCCI
PC BOARD AVCC
PC BOARD OVCC
PC BOARD AGND
FERRITE-BEAD
SUPPRESSORS
PC BOARD OGND
AVCCR
AVCCI
OVCCQ
OGNDQ
OGNDI
OVCCI
OVCCI, OVCCQ
OVCCI
OVCCQ
OGNDQ
OGNDI
OVCCI
NOTE:
LOCATE ALL 47pF AND 10nF CAPACITORS, WHICH DECOUPLE AVCCI, AVCCQ, AVCCR, OVCCI, AND OVCCQ AS CLOSE
AS POSSIBLE TO THE CHIP. IT IS ALSO RECOMMENDED TO CONNECT ALL ANALOG GROUND CONNECTIONS TO A COMMON ANALOG
GROUND PLANE AND ALL DIGITAL GROUND CONNECTIONS TO ONE COMMON DIGITAL GROUND PLANE ON THE PC BOARD. A SIMILAR
TECHNIQUE CAN BE USED FOR ALL ANALOG AND DIGITAL POWER SUPPLIES.
AVCC = AVCCI = AVCCQ = AVCCR = +5V
±5%
OVCCI = OVCCQ = +3.3V
±10%
10nF
47pF
4 x 10nF
10nF
47pF
10
F
10nF
10
F
10nF
47pF
10nF
47pF
MAX105
Figure 9. MAX105 Decoupling, Bypassing and Grounding
